This competing revised application is for renewing P01-HL31950-26A1 (years 26-30). Three projects and two cores will combine efforts to advance understanding of the mechanisms underlying thrombosis and thrombotic diseases and new knowledge from this Program may define new therapeutic strategies for reducing disease burden. Project 1 (Griffin: Murine protein C and protein S proof of principle research) will focus on the initiation of signaling by activated protein C (APC) via apoER2 and Dabi in mice; on the structural elements of apoER2 that regulate its interactions with APC; and on a possible role for Dabi in APC-dependent mortality reduction in murine sepsis or antithrombotic activities in vivo. Novel APC mutants with selective loss of interaction with only one of its receptors (apoER2, PARI, or EPCR) or with the cofactor, protein S, will be engineered for evaluating consequences on inflammation and thrombosis, and the in vivo antithrombotic actions of protein S will be explored in murine thrombosis models. These highly synergistic aims will address critical knowledge gaps in the understanding of the mechanisms that initiate and regulate the response to vascular injury. Project 2 (Ginsberg: Adhesive signaling and vascular thromboresistance) will test the hypotheses that CD98 is important in the proliferation and function of cells in injured blood vessels, and that localized activation of Protein Kinase A in endothelial cells regulates cell alignment and migration through the phosphorylation of substrates, including integrin a4, and the resulting modification of Rho GTPase activities. Project 3 (Ruf: Regulation of tissue factor (TF) procoagulant properties in thrombosis) will test the hypotheses that TF procoagulant activity on cells is regulated by interactions with integrins and modulated by protease-activated receptor 2 (PAR2) signaling, and that the P2X7 receptor contributes to modulating TF activation releasing active TF-bearing micro particles from the vessel wall and into the intravascular compartment. Two Cores will provide support for all three Projects in terms of murine thrombosis in vivo model studies and administrative matters. New knowledge will contribute to improving prevention, diagnosis and treatment of relevant diseases related to thrombosis.